Osmotic-activated drug delivery systems MCQs With Answer

Osmotic-activated drug delivery systems MCQs With Answer

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Introduction

Osmotic-activated drug delivery systems (OADS) are precision-controlled oral platforms that use osmotic pressure to deliver drugs at a predictable, often zero-order rate. For M. Pharm students studying Drug Delivery Systems (MPH 102T), mastering OADS—such as elementary osmotic pumps (EOP), push–pull osmotic pumps (PPOP), controlled-porosity systems, and advanced OROS technologies—is essential for robust formulation and therapeutic design. This MCQ set explores principles of osmotic pressure, semipermeable membranes, pore formers, wicking agents, coat engineering, orifice design, kinetics, and evaluation parameters. It also integrates case-based reasoning, formulation strategy for drugs of varying solubility, and marketed examples. Use these questions to test your conceptual depth and application skills in osmotic delivery system design.

Q1. In an elementary osmotic pump (EOP), which component primarily governs water influx into the core?

  • Laser-drilled delivery orifice
  • Semipermeable membrane made of cellulose acetate
  • Wicking agent such as microcrystalline cellulose
  • Osmogen like sodium chloride inside the core

Correct Answer: Semipermeable membrane made of cellulose acetate

Q2. The major advantage of osmotic systems over diffusion-controlled reservoir systems is their:

  • Ability to deliver poorly soluble drugs without any formulation modification
  • Release rate independence from gastrointestinal pH and agitation intensity
  • Capability to bypass first-pass metabolism entirely
  • Complete elimination of dose dumping even if the coat ruptures

Correct Answer: Release rate independence from gastrointestinal pH and agitation intensity

Q3. Which statement best describes the push–pull osmotic pump (PPOP)?

  • Monolayer core releasing drug solution through multiple laser-drilled orifices
  • Bilayer or trilayer core with a drug layer(s) and a swellable polymeric push layer
  • Diffusion-controlled matrix with insoluble polymer and pore former
  • Multiparticulate pellets coated with enteric polymer and immediate-release outer coat

Correct Answer: Bilayer or trilayer core with a drug layer(s) and a swellable polymeric push layer

Q4. In controlled porosity osmotic pumps (CPOP), the primary role of the pore former (e.g., sorbitol, NaCl) in the coating is to:

  • Plasticize the membrane and increase elasticity
  • Create micropores upon leaching to eliminate the need for laser-drilled orifices
  • Increase osmotic pressure within the core
  • Chemically react with the drug to enhance solubility

Correct Answer: Create micropores upon leaching to eliminate the need for laser-drilled orifices

Q5. For a highly water-soluble drug administered via EOP, which change is most likely to decrease the release rate while maintaining zero-order behavior?

  • Increasing the coat thickness of the semipermeable membrane
  • Increasing the orifice diameter from 0.4 mm to 1.2 mm
  • Adding a wicking agent to the core
  • Reducing the level of osmogen (e.g., NaCl) in the core

Correct Answer: Increasing the coat thickness of the semipermeable membrane

Q6. Which is a typical polymer used as the semipermeable membrane in osmotic pumps?

  • Ethyl cellulose
  • Cellulose acetate (e.g., CA 398-10)
  • Hydroxypropyl methylcellulose K100M
  • Polyvinylpyrrolidone K30

Correct Answer: Cellulose acetate (e.g., CA 398-10)

Q7. The primary function of a wicking agent (e.g., microcrystalline cellulose, colloidal silica) in an osmotic core is to:

  • Enhance membrane flexibility
  • Facilitate water penetration and maintain drug suspension formation
  • Increase osmotic pressure of the core
  • Prevent dose dumping by plugging the orifice

Correct Answer: Facilitate water penetration and maintain drug suspension formation

Q8. Which formulation strategy is most appropriate for a poorly water-soluble drug intended for once-daily, pH-independent delivery?

  • Elementary osmotic pump with no excipients
  • Push–pull osmotic pump with high-MW polyethylene oxide in push layer
  • Immediate-release tablet with surfactant
  • Matrix tablet using ethyl cellulose

Correct Answer: Push–pull osmotic pump with high-MW polyethylene oxide in push layer

Q9. Which factor is least likely to significantly affect the in vitro release rate of a robust osmotic pump?

  • Agitation speed in USP Apparatus 2 (50 vs 100 rpm)
  • Semipermeable membrane permeability
  • Osmotic pressure gradient across the membrane
  • Coat weight gain (membrane thickness)

Correct Answer: Agitation speed in USP Apparatus 2 (50 vs 100 rpm)

Q10. For laser drilling of orifices in OROS systems, which is commonly used in manufacturing?

  • CO₂ laser at 10.6 μm wavelength
  • Nd:YAG laser at 355 nm exclusively
  • Ultrasonic drilling with solvent assistance
  • Mechanical micro-punch

Correct Answer: CO₂ laser at 10.6 μm wavelength

Q11. Which marketed product exemplifies a trilayer OROS system with ascending release for ADHD management?

  • Glucotrol XL (glipizide)
  • Concerta (methylphenidate)
  • Procardia XL (nifedipine)
  • Ditropan XL (oxybutynin)

Correct Answer: Concerta (methylphenidate)

Q12. In an osmotic system, excessively increasing the orifice diameter is most likely to result in:

  • Maintenance of strict zero-order release with no change
  • Shift from osmotic pumping to diffusion/erosion-dominated release
  • Immediate plugging of the orifice by push-layer polymers
  • Bursting of the tablet due to internal pressure

Correct Answer: Shift from osmotic pumping to diffusion/erosion-dominated release

Q13. The release rate from an EOP is approximately proportional to which parameter, assuming a saturated drug solution is maintained in the core?

  • Membrane area-to-thickness ratio
  • Square of the orifice radius
  • Square root of drug solubility
  • Core compression force

Correct Answer: Membrane area-to-thickness ratio

Q14. Which coating excipient primarily acts as a plasticizer for cellulose acetate membranes in osmotic systems?

  • Polyethylene glycol 400
  • Sodium chloride
  • Sorbitol
  • Lactose monohydrate

Correct Answer: Polyethylene glycol 400

Q15. OROS-CT (colon-targeted) systems achieve site-specific delivery mainly by:

  • Using only a thicker semipermeable membrane to delay release
  • Employing an enteric outer coat to provide a lag, then osmotic pumping in the colon
  • Utilizing colonic bacterial enzymes to open the orifice
  • Designing multiple large orifices that open at high pH

Correct Answer: Employing an enteric outer coat to provide a lag, then osmotic pumping in the colon

Q16. Which is the most appropriate role of sodium chloride in an osmotic core for a moderately soluble drug?

  • Reducing membrane permeability
  • Acting as an osmogen to maintain a high osmotic pressure gradient
  • Forming the semipermeable membrane
  • Preventing wicking into the core

Correct Answer: Acting as an osmogen to maintain a high osmotic pressure gradient

Q17. Asymmetric membrane capsules used as osmotic systems differ from laser-drilled tablets primarily because they:

  • Contain no semipermeable layer
  • Develop in situ microporosity through phase inversion without laser orifices
  • Release drug only by erosion
  • Require gastrointestinal enzymes for activation

Correct Answer: Develop in situ microporosity through phase inversion without laser orifices

Q18. Which change would most likely reduce the risk of dose dumping in a CPOP formulation?

  • Excessively increasing pore former concentration
  • Optimizing coat weight to balance permeability and mechanical integrity
  • Using a highly brittle membrane without plasticizer
  • Drilling multiple large orifices

Correct Answer: Optimizing coat weight to balance permeability and mechanical integrity

Q19. For a drug with very high solubility that tends to crystallize upon hydration in the core, which approach best sustains zero-order release?

  • Add precipitation inhibitors/solubilizers to maintain a saturated solution
  • Drill a larger orifice to prevent supersaturation
  • Remove osmogen from the core
  • Use an enteric coat only

Correct Answer: Add precipitation inhibitors/solubilizers to maintain a saturated solution

Q20. Which evaluation outcome most confirms osmotic control rather than diffusion control in vitro?

  • Significant increase in release rate with increased agitation speed
  • Release rate proportional to square root of time
  • Near-constant release rate across different pH media and agitation speeds
  • Complete dependence on orifice size beyond 1.5 mm

Correct Answer: Near-constant release rate across different pH media and agitation speeds

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